Objective : Motor learning has been traditionally defined as the acquisition of skilled movements through physical practice. An increasing number of investigations have recently studied the effect of imagery practice and the relationship between actual and imagined practice. Thus, the purpose of the present study is to compare the effects of physical practice and mental imagery training on the sequential motor task. Methods : Total of fifty college students(25 males) participated in the experiment with written informed consent, who had no history of neurologic or visual deficits. Subjects were randomly assigned to three groups(mental, physical, and control group). Different subjects participated in each experiment. Subjects were asked to press the matched button as quickly and accurately as possible, when one of five colored lights was displayed on computer screen(red, yellow, green, blue). Reaction time was recorded during five randomly ordered blocks at the pre and post test in all groups. Results : A repeated measurement of two way ANCOVA showed that there was significant difference in a main effect of group and interaction of group by pre-post test, but not in a main effect of pre-post test. And there was a difference in the between group comparison in post-hoc analysis, which showed a great reduction in RT for mental and physical training groups compared with control group. Conclusion : The findings reveal that the improvement of the motor skill occurred in both mental and actual practice, and mental imagery training is as much effective as the actual training. The sequential motor task through motor imagery practice improves performance by acting both on the preparation and anticipation on execution of movements. Motor imagery training might provide great benefits with brain damaged patients who could not perform the actual movement, by practicing virtual tasks that required motor planning and execution.